The present invention relates to a nozzle assembly, comprising at least one nozzle for the injection of a liquid moistening medium into a flue-gas flow especially for cooling the flue gas and a body for delivering the moistening medium to the nozzle, the nozzle and body being essentially disposed in a flue-gas flow duct or the like.
Cooling of a flue-gas close to the dew point is effected by injecting into a flue-gas flow in a flue-gas moistening reactor some flue-gas moistening medium, generally water, which contains minor amounts of additives. The presently available assemblies employing a generally tubular body, disposed in a flue-gas flow duct and fitted with at least one nozzle are not advantageous. Flue gases contain solids such as fly ash or flue-dust and Ca-compounds, which lead to the soiling and blocking of nozzles. This problem is particularly pronounced in cooling a flue gas whenever the purpose is to cool the gases close to the dew point. Then, the following reasons may cause the soiling of nozzles and a body:
a flow of flue gas creates eddies (back-eddies) around a pipework with a result that solids and water drift into and get stuck on a pipe-work, PA1 the water in flue gas condenses on cold nozzle tubes with a result that solids stick to the surface of a moist tube, and PA1 direct splashing of water from nozzles onto a body with a result that the surfaces get wet and soiled.
Another problem is a corrosion hazard of nozzles and a body as flue gases often contain sulphur whose reactions at temperatures close to the dew point cause acid corrosions.
In the flue-gas flow duct of a flue-gas moistening rector there occures slagging (accumulation of solids on the walls of a flow duct) also in the upper portions of a reactor, which is why the reactor must be periodically mechanically cleaned for example at 8 hour intervals. The falling pieces of slag result in a hazard of damaging the nozzle assembly as they hit it.
A satisfactory solution has not been found to the above problems in the presently available nozzle assemblies.